I have a very low opinion of thatmodle; of tire and that brand of tire. They don't make any tires that aren't $300 that are worth a hoot.
From the sound of thing they have uniformly wore out in less than 20k. It speaks to the tire or the driver although you would have to be a very skillfull driver to use up tires evenly that fast (bg).
Bosch Master, ASE Master, L1
33 years MB technician